It's easy enough to make a bike look like crap. You just can't be prissy about your parts. I have a frame that I sanded and spray painted flat black. No clear coat. The spray paint will get wear points fairly quickly. That's good. Some stickers will help too. I have a Chris King headset. The first thing I did after installing it was take sand paper to it and get rid of the name. It looks like crap now. Same goes for my derailers. Electrical tape covers the Shimano SLX on my cranks, so they're just all black, wrapped in black tape now. If you're not worried about "ruining" some nice, new parts, your bike can look pretty crappy very easily. Even if a thief did recognize some nice parts, you don't want them to have any resale value. Taking away quick sale value is the first step to keeping your bike from getting stolen.